build documentation refactoring (#395)

BUILD_WINDOWS.TXT, BUILD_UNIX.TXT removed from root folder

src/BUILD_WINDOWS.TXT, src/BUILD_UNIX.TXT converted to "md"

BUILD_WINDOWS.TXT, BUILD_UNIX.TXT are now hyperlinks in README.md

src/BUILD_UNIX.md

@@ -0,0 +1,148 @@
+How to build SoftEther VPN for UNIX
+===================================
+
+
+Requirements
+------------
+
+You need to install the following software to build SoftEther VPN for UNIX.
+
+- Linux, FreeBSD, Solaris or Mac OS X.
+- GNU Compiler Collectipon (gcc) and binary utilities.
+- GNU Make (gmake).
+- GNU C Library (glibc).
+- POSIX Threads (pthread).
+- OpenSSL (crypto, ssl).
+- libiconv.
+- readline.
+- ncurses.
+
+For example, the following commands help you to install the above programs
+on Fedora or CentOS Linux:
+```
+$ yum -y groupinstall "Development Tools"
+$ yum -y install readline-devel ncurses-devel openssl-devel
+```
+
+
+How to Build
+------------
+
+To build the programs from the source code, run the following commands:
+
+```
+$ ./configure
+$ make
+```
+
+If any error occurs, please check the above requirements.
+
+
+How to Install SoftEther VPN Server, Bridge or Client
+-----------------------------------------------------
+
+To install the vpnserver, vpnbridge and vpnclient programs into the
+/usr/bin directory, run the following as the root user:
+
+```
+# make install
+```
+
+After the installation will complete successfully:
+
+- Execute 'vpnserver start' to run the SoftEther VPN Server background service.
+- Execute 'vpnbridge start' to run the SoftEther VPN Bridge background service.
+- Execute 'vpnclient start' to run the SoftEther VPN Client background service.
+- Execute 'vpncmd' to run SoftEther VPN Command-Line Utility to configure
+  VPN Server, VPN Bridge or VPN Client.
+
+- You can also use VPN Server/Client Manager GUI Tool on other Windows PC to
+  connect to VPN services remotely.
+  You can download the GUI Tools from http://www.softether-download.com/.
+
+
+How to Run SoftEther VPN Server for Test
+----------------------------------------
+
+To start the SoftEther VPN Server background service, run the following:
+
+```
+$ bin/vpnserver/vpnserver start
+```
+
+To stop the service, run the following:
+
+```
+$ bin/vpnserver/vpnserver stop
+```
+
+To configure the running SoftEther VPN Server service,
+you can use SoftEther VPN Command Line Management Utility as following:
+
+```
+$ bin/vpncmd/vpncmd
+```
+
+Or you can also use VPN Server Manager GUI Tool on other Windows PC to
+connect to the VPN Server remotely. You can download the GUI Tool
+from http://www.softether-download.com/.
+
+
+How to Run SoftEther VPN Bridge for Test
+----------------------------------------
+
+To start the SoftEther VPN Bridge background service, run the following:
+
+```
+$ bin/vpnbridge/vpnbridge start
+```
+
+To stop the service, run the following:
+
+```
+$ bin/vpnbridge/vpnbridge stop
+```
+
+To configure the running SoftEther VPN Bridge service,
+you can use SoftEther VPN Command Line Management Utility as following:
+
+```
+$ bin/vpncmd/vpncmd
+```
+
+Or you can also use VPN Server Manager GUI Tool on other Windows PC to
+connect to the VPN Bridge remotely. You can download the GUI Tool
+from http://www.softether-download.com/.
+
+
+How to Run SoftEther VPN Client for Test
+----------------------------------------
+
+To start the SoftEther VPN Client background service, run the following:
+
+```
+$ bin/vpnclient/vpnclient start
+```
+
+To stop the service, run the following:
+
+```
+$ bin/vpnclient/vpnclient stop
+```
+
+To configure the running SoftEther VPN Client service,
+you can use SoftEther VPN Command Line Management Utility as following:
+
+```
+$ bin/vpncmd/vpncmd
+```
+
+Or you can also use VPN Client Manager GUI Tool on other Windows PC to
+connect to the VPN Client remotely. You can download the GUI Tool
+from http://www.softether-download.com/.
+
+
+************************************
+Thank You Using SoftEther VPN !
+By SoftEther VPN Open-Source Project
+http://www.softether.org/