Macaulay2 interface update/improvement for version 1.3.1

[novoselt]

See also #5467 and #7915 (!).

These patches change the prompt detection/stripping and update doctests to cause no errors with Macaulay2 1.3.1.

Improvements/fixes achieved:

• examples in Macaulay2 documentation (which include input prompts) do not break the interaction with Sage;
• empty/whitespace/comment lines can be executed;
• multiline commands can be executed;
• stripping output prompts will not cut error messages if they occur (e.g. the first call "help Thing" currently shows some errors in Macaulay2);
• "macaulay2.restart()" does not print a useless variable name.

This is done by:

• changing input and input continuation prompts;
• starting with a big line number to make all output labels of the same width;
• making sure that only output labels and spaces are stripped from the output.

These patches make tickets #7882 and #7888 unnecessary.

[novoselt]

I changed my mind about importance of "restart" command in the middle of the code after seeing a talk today. So the patch is rewritten to allow it everywhere. All doctests still pass with both patches applied.

[novoselt]

Renamed patches and commit messages to follow conventions. Apply both patches starting with "trac_7897"

[mhansen]

Looks good to me.

[mhansen]

Also apply #5467 and #7915.