Writing style improvements

Edit texts in the game to be more consistent.

[x] You must (a) purchase a card, (b) play a technique, (c) build a stack, or (d) take an inventory action [Inventory Action] → You must play a technique, purchase, build, or [Take an inventory action]
[x] You must select cards to build in stack 1 [Confirm Selection] [Cancel] → You must select cards to build stack 1 [Build with selected] [Cancel]
[x] You must discard any number of cards [Discard Selection] [Cancel] → You must select any number of cards to discard [Discard selected] [Cancel]

[x] Your own deck popup: Sami's Deck → Your deck (remove Title Case too)
[x] Your own discard popup: Sami's Discard → Your discard (remove Title Case too)
[x] Remove Title Case:
- [x] Player 1's Deck → Player 1's deck
- [x] Player 1's Discard → Player 2s discard

Whebon / dale-of-merchants