Upgrade documentation

[sarthakpati]

See reference: https://github.com/TartanLlama/cpp-documentation-example

[sarthakpati]

Although documentation is now available online and in the same format as we distribute CaPTk's documentation, this mechanism needs a lot of improvement. Closing out this issue for now.

[sarthakpati]

Another resource to look at: https://github.com/robotology/ycm