Support for self signed certificate (HTTPS)

Support for self signed certificate (HTTPS)

Add possibility to disable ssl verification, just as i can do with git
using: git config --global http.sslVerify false

To enable the feature, configure
Window->Preferences->Team->Git->Configuration
and add a new key/value: http.sslVerify=false

When handling repos over https, JGit will then check that flag to see
if security is loose and the ssl verification should be ignored.

Having it implemented as a key/value makes it not too obvious in the
GUI - so the user must know what he/she is doing when adding it. Being
aware of the risks etc.

Bug: 332487
Change-Id: I2a1b8098b5890bf512b8dbe07da41036c0fc9b72
Signed-off-by: Matthias Sohn <matthias.sohn@sap.com>