[release] Prepare for next development iteration

Change-Id: Ic32e00e1f798a438f76b9f19a00dce094cc6800d
Add more libraries to the list of build time dependencies

Added libboost-test-dev, libjsoncpp-dev and libsctp-dev
Also warn that the dependency list is changeable
and point to the dependency list used for building.

Change-Id: Ia01f0626b231ff0e2c13c9ae15576e99082f90a6
Remove stray debug print statement

Change-Id: I8df486e185307e5e4e89cc8726bf52cd93ef4659
Use semantic markup for mimetypes and (mail)headers

So that we can index or markup them selectively in the
future.

Change-Id: I9038e946a8b1482a9d9a690395d3dc0eab6a442d
Use the literal or :samp: role for code examples including variables

Reformat uses of bold for variables, and also state
it in the "conventions" section

Change-Id: I4ac0c4b5c9138792a6aac5295b3f8c2e39d6dbbb
[release] 4.2.2

Change-Id: Ibfddb21becaa254c6e16bc9c08abc13d47dd142f