Make a full copy of the parser and apply our modifications to it

[kgyrtkirk]

To enable easier access to enhance the parser - instead of copying parts of it this PR proposes to keep a full copy with our modifications in the repo. This makes:

• a more easier to understand build
• the build will unpack the "base" version of the parser to sql/target/calcite-base-parser ; so its relatively easy to see what have changed
• more freedom on what could be modified later
• upgrade is "different":
  • this PR contains a script which could help during upgrades (dev/updgrade-calcite-parser)
  • it restores the parse into the original state and apply our modifications and the updated ones and then merge it - this process should more or less finish successfully

[kgyrtkirk]

@rohangarg @gianm @clintropolis: I wonder if you could take a look?