util: Implementing conversion to/from system_clock::TimePoint with customized format

Change-Id: I879cf2b3fe7402c4600e3536b02147333f5b9620
Refs: #1454
docs: Importing initial set of library documentation from wiki

To build documentation, doxygen (+graphviz dot) and sphinx-build are
required.  Manpages are build and installed during `./waf build` stage
if sphinx-build is present.

Documentation can be build using the following commands:

    # Full set of documentation (tutorials + API) in build/docs
    ./waf docs

    # Only tutorials in `build/docs`
    ./waf sphinx

    # Only API docs in `build/docs/doxygen`
    ./waf doxgyen

Change-Id: I4c08be08ca3e22068db54584f99467aa6cf38d04
Refs: #1462
security: Fix Validator::verifySignature bug

Refs: #1467

Change-Id: I2b69ccf15ede35c8b201c74ddf786e7b136fe421