Tweak function names, code, table content, etc.

[sogaiu]

This PR contains a variety of suggestions (trying to align with this).

Among other things it contains:

• Changes to some code samples for consistency (e.g. tweak some naming, avoiding shadowing of built-in names, comments matching actual behavior, etc.)
• Changes to some identifiers (e.g. fiber/root instead of fiber/root-fiber, math/nan instead of NaN)
• Changes to one of the PEG tables (e.g. adding some missing info, swapping order of two rows, fixing the table where a row had leaked out, etc.)
• Change "Janet Package Manager" to "Janet Project Manager" to match the name in the jpm repository

[sogaiu]

Also removed eqn aka JOP_NUMERIC_EQUAL as it was removed from janet here.