add version cmd

[rawdaGastan]

Add a get version command for backend

[Rodina222]

The server should be build as follows in order to get the latest version and commit of the app:

go build -ldflags "-X 'github.com/codescalersinternships/Flyspray/cmd.commit=$(shell git rev-parse --short HEAD)' -X 'github.com/codescalersinternships/Flyspray/cmd.version=$(shell git describe --abbrev=0 --tags)'"

Where,

• git rev-parse --short HEAD: This command retrieves the short hash of the latest commit in the repo. It assigns the value to github.com/codescalersinternships/Flyspray/cmd.commit variable.
• git describe --abbrev=0 --tags: This command retrieves the latest annotated tag in the repo It assigns the value to github.com/codescalersinternships/Flyspray/cmd.version variable.