Support all of MySQL's comparison operators

[p810]

p810\MySQL\Builder\Grammar\Where and p810\MySQL\Builder\Grammar\Join currently only support a small subset of the possible comparison operators that MySQL provides. This effort will be to implement the remaining operators as methods of either trait, and add test cases for each.

p810\MySQL\Builder\Grammar\Where

Methods
whereNotLike()
orWhereNotLike()
whereBetween() [1]
orWhereBetween()
whereNotBetween()
orWhereNotBetween()
whereIs()
orWhereIs()
whereIsNot()
orWhereIsNot()
whereIsNull()
orWhereIsNull()
whereIsNotNull()
orWhereIsNotNull()
whereGreatest()
orWhereGreatest()
whereLeast()
orWhereLeast()
whereInterval()
orWhereInterval()
whereCoalesce()
orWhereCoalesce()
whereNullSafeEquals() [2]
orWhereNullSafeEquals()

^[1] This method, whereNotBetween(), and their or* aliases, will also have *Many() variants that support lists of BETWEEN or NOT BETWEEN queries.

^[2] This method and its or* alias will have aliases named whereNullSafe() and orWhereNullSafe() for API consistency, since the default operator with where() is the non-null safe equals (=)

p810\MySQL\Builder\Grammar\Join

Methods
onLess()
orOnLess()
onLessOrEqual()
orOnLessOrEqual()
onGreater()
orOnGreater()
onGreaterOrEqual()
orOnGreaterOrEqual()
onLike()
orOnLike()
onNotEquals() [1]
orOnNotEquals()
onNotLike()
orOnNotLike()
onBetween()
orOnBetween()
onNotBetween()
orOnNotBetween()
onIs()
orOnIs()
onIsNot()
orOnIsNot()
onIsNull()
orOnIsNull()
onIsNotNull()
orOnIsNotNull()
onGreatest()
orOnGreatest()
onLeast()
orOnLeast()
onInterval()
orOnInterval()
onCoalesce()
orOnCoalesce()
onNullSafeEquals() [2]
orOnNullSafeEquals()

^[1] This will also include onNot() and orOnNot() for consistency with the API provided by p810\MySQL\Builder\Grammar\Where.

^[2] This method and its or* alias will have aliases named onNullSafe() and orOnNullSafe() for API consistency, since the default operator with on() is the non-null safe equals (=)

[p810]

Updated the list with a couple changes:

1. Comparison functions like GREATEST() will be implemented as their own standalone functions in the top level of the project's namespace (e.g. p810\MySQL\greatest()) since these are not specifically operators used in queries. They could be manually written into a clause but I like the thought of having helpers for certain functions, which make sense in a query builder since the goal is bringing the writing of SQL queries closer to the language.

2. The *Many() variants have been scrapped since they represent an uncommon use case and introduce a level of complexity that's unnecessary when they can easily be written using helper methods like commas() or just by hand.