Fixed MacOS, removed page-term-agent hack

• Fixed MacOS problems
• Removed FreeBSD release as it's currently not supported by cross (it still should be possible to build page from sources)
• PTY path is obtained from &channel variable - no more page-term-agent binary required
• Less dependencies - better build time - smaller binary size
• Updated code, added comments
• Added -P option to set $PWD as working directory for output buffer
• Better error messages
• Updated dependencies