Ongoing development II

[Pathoschild]

This pull request contains ongoing development since the last official update in August 2017 to maintain compatibility with the latest versions, update for new SMAPI features, and make minor improvements.

Changes

Continuing from the changes in PR #10...

• Updated for Stardew Valley 1.4+, SMAPI 3.0+, and unofficial 64-bit mode.
• Standardised config.json format.
• Updated for changes in Luck Skill and Magic.
• Fixed Cooking/Magic adapters incorrectly checking for Luck Skill mod.
• Fixed painless prestige for custom skills that don't use Game1.player.experiencePoints (like Cooking Skill and Magic).
• Fixed level up menu not exiting correctly.
• Fixed level-up menu coming up every night once you prestige in non-painless mode and level up back to at least level 5.
• Updated the mod build package and migrated to the new simplified .csproj format.
• Internal refactoring.

Testing

The unofficial updates for Skill Prestige have over 20,000 downloads (not counting adapter downloads), so the changes should be pretty stable. See download counts for the most recent releases: unofficial.14, unofficial.13, unofficial.12, unofficial.11, unofficial.10, unofficial.9, unofficial.8, unofficial.7 (for 1.4 alpha), unofficial.6, unofficial.5, unofficial.4, unofficial.3, unofficial.2, unofficial.1.

Let me know if you want me to change anything!