Add command LSP

This is a fairly extensive refactoring of lsp-tester in order to support LSPs that are launched as sub-processes and communication via standard input and output.

• Refactoring of Receiver as an interface supporting:
  • TCP protocol which already existed and
  • Sub protocol to support sub-process LSPs.
• New -mode and -protocol flags to support wider variety of test cases.
• Various new flags and flag behavior:
  • configuration files containing flags
  • -fileLevel
• Various bug fixes