Pull escape sequences into their own named file

[Tyriar]

Organize escape sequences constants into a new EscapeSequences.ts file that gives them names and centralizes the values.

TODO:

• C0 codes Pull C0 escape sequences into its own file #461
• Replace all references to C0 codes in xterm.js Pull C0 escape sequences into its own file #461
• CSI codes
• Replace all references to CSI codes in xterm.js
• OSC codes
• Replace all references to OSC codes in xterm.js

[Tyriar]

The current layout is good