Added schema caching to Schema.cs
Added schema caching to Schema.cs

How it works:
Schema web connection is opened and headers read.
If cache file is not present or its creation time is older than "Last-Modified" of web schema Schema is pulled from api.steampowered.com, put into cache file and  cache file creation time is set equal to Schema Last-modified.
If cache file is present and is up-to-date the Schema is downloaded from the file.
Update SteamTrade/Schema.cs

Fixed indentation, changed cache file name.
Change Output Path of SteamBot.

- Output path now matches documentation. Goes to <projectroot>/Bin
- Update README with more information and remove old information.
- Remove old SLN file and add a configuration template file for release
builds.
Added extra error checking before adding item to trade
Fix for wrong bot behaviour being used.
Fixed Bug on RemoveAllItemsByDefindex().
- It wasn't removing any items.
- note: bug introduced in ce285d96e9a9f9b00b685ad925e0fe7347829757 along with RemoveAllItemsByDefindex().
Updates SteamKit2 Dependency
Implemented OnFriendRemove() callback.
Removed OnFriendRemove() remark in the in-line documentation.
Adds IsFreeToPlay() To Inventory.cs #67

Creates a method to check if a user's inventory is free to play. This
fixes Issue #67: https://github.com/Jessecar96/SteamBot/issues/67

Tested on my inventory, and a free to play's inventory.

This does take into effect the comment of a Free to Play can use
Backpack Expanders.
Revert "Adds IsFreeToPlay() To Inventory.cs #67"

This reverts commit 0b0c85fdb8c8f951e3de1a2e3f1ecf52e9cdbb49.
Adds IsFreeToPlay()

Adds a function to determine if a user is FreeToPlay or not.
float_value attribute allows user to get the number of a crate in trade
contained_item attribute allows user to get the contents of a wrapped gift item in trade
Changed contained_item type to Item
Moved contained_item to its proper place
Updated SteamKit2 dependency to fix long connection times on startup
Added functions to get inventories when not in a trade
Added functions to get inventories when not in a trade