Add synchronized and synchronized major mode

[matthias-reis]

Two more processing modes should be added as follows:

• synchronized: updates all dependencies always to exactly the same version number - this should also work with normal repos
• synchronizedMajor: updates all packages to exactly the same Major version as soon as any package comes up with a breaking change - useful for quickly viewing connected packages by major version (like babel does it)

this refactoring heavily depends on #29