Port REDCapR wrapper functions from rcc.grace

[pbchase]

In the rcc.grace project, I made three functions that wrap REDCapR functions adding parameters that support REDCap custodian authentication methods. Copy those function into redcap custodian. Those functions are

• read_project_data.R
• read_project_metadata.R
• write_project_data.R

They have no test code, so you can just copy them to ./R/, build the docs, and check the package.

[ChemiKyle]

Addressed by #148