Adds a feature which auto-save's at the start of every singleplayer mission.

[CCHyper]

Closes #148

This pull request adds the feature from Red Alert 2 which auto-save's at the start of every singleplayer mission. This can be used as a checkpoint to jump between any mission previously played.

This feature can be disabled by adding the following to the [Settings] section in VINIFERA.INI; AutoMissionSaveEnabled=no

NOTE: Due to the vast inconsistency between the scenario descriptions and MISSION.INI descriptions, each of the standard Tiberian Sun and Firestorm campaign missions requires fixing-up to ensure the save file descriptions are consistent. The new descriptions used are based on observations in the "Prima's Official Guide" and the most correct grammatical text in the game.

If you wish to disable this feature, you can add the following to the [Settings] section in VINIFERA.INI; FixAutoMissionSaveDescriptions=no