Rebase parameters branch on current master.

* Change parameters const& to const parameters& for coding style.
* Update thumbnail producer to use parameters class.
* Update some methods to use params.get(...) rather than get_params.

Conflicts:
	core/core.vcxproj
Merge pull request #138 from cambell-prince/master_parameters1

Rebase parameters branch on current master.
Misc changes
Merge branch 'master' of https://github.com/CasparCG/Server
Some refactoring based on the new parameters class
Misc refactoring and fixes