v1.1.1: Makefile: inject Git version to main program

Silly mistake: I forgot to inject Git version to main program on build;
thus, everyone running v1.1.0 got "Vanadia version: HEAD" when running
`./vanadia -v`.

v1.1.0: main: Add -v flag

As Vanadia can be integrated into any automated workflow, some tools
may do "./vanadia -v" to ensure that Vanadia is in the right version
(otherwise, the tool may download newer version of Vanadia).

v1.0.0

postman: Make HostToEnv variable name configurable