Added missing moment and moment.utc overloads.

- Added moment(string, string?, boolean?) overload for specifying date,
format and strict parsing flag.

- Added moment(string, string?, string?, boolean?) overload for
specifying date, format, language and strict parsing flag.

- Added moment(string, string[], boolean?) overload for specifying date,
multiple formats and strict parsing flag.

- Added moment(string, string[], string?, boolean?) overload for
specifying date, multiple formats, language and strict parsing flag.

- Modified parameter names for moment.utc(...) methods to match those
for the similar moment(...) method overloads.

- Ensured all moment(...) methods have a moment.utc(...) equivalent.

- Added tests for all newly added overloads.

- Added missing tests for some existing overloads.