Definite Integration

[JooseMann]

Add support for Definite Integration with Expression.
Checklist:

• Add Substitution of a Real as a bound into the Expression after it is integrated indefinitely
• Support for combining expressions within Definite Integrals
  • Equal limits of integration (0 to 0) is always defined as 0
  • Support for swapping limits of integration and negating the expression
  • Simplification with functions being even or odd
  • Combining Definite Integrals with shared bounds (e.g. an integral from 0 to 3 added to another from 3 to 5 can be written as one from 0 to 5)

[JooseMann]

Many of the previously listed goals ultimately ended up being wasteful. In particular, swapping limits of integration and negating the expression was an extra check for no benefit (as computing the difference was equally as fast with swapped bounds as normally), and identifying a function as even or odd would be much more difficult than just computing the definite integral normally.

For those reasons, those implementations were not added, in favor of a more general definite integration method.