Improve the equation language

[bdezonia]

There is lots of room for expansion in the equation language:

• vec_or_mat_or_ten raised to the int_power
• number * vec/mat/ten
• factorial
• erf/erfc (Done? If not then easily doable I think)
• atan2
• matrix constants whose dims are not 0x0 (imagine declaring it as PI(2) or E(3) in language to give it a square 2x2 or 3x3 shape)
• parsing and assigning -minint correctly (Done I think)
• supporting tuples
• supporting a/rgbs
• supporting points
• supporting booleans and also and/or/not/shift
• like the E(5) and PI(3) we can do rand(7,7) for a 7x7 matrix of random values in the parsing language.
• ramp function
• step function
• etc.