add evaluate context manager
Extend use of global_evaluate
Add cacheit decorator back onto AssocOp.__new__
cacheit inspects global variables
Extend global_evaluate

Find cases like def foo(..., evaluate=True)
FiniteSet plays well with evalaute=False
fix typo for global_evaluate
small docstring for evaluate context manager
Move powsimp assertion to tests
Merge branch 'master' into with-evaluate

Conflicts:
	sympy/geometry/point.py
docstring for evaluate context manager
Merge branch 'master' into with-evaluate
Merge branch 'with-evaluate' of github.com:mrocklin/sympy into with-evaluate

Conflicts:
	sympy/core/evaluate.py
evaluate=None means trust global, not False

This was assumed in a test.  I'm unassuming it.  Hopefully no one cares
Workaround Dummy's printing in Subs constructor (fixes #7068)
Add test for issue 7068
Make `orientnew` respect parent class
Added slices to the prime sieve.

The following syntax is now possible when using the prime sieve:

```python
from sympy import sieve

assert sieve[5] == 11
assert list(sieve[5:10]) == [sieve[x] for x in range(5, 10)]
assert list(sieve[5:10:2]) == [sieve[x] for x in range(5, 10, 2)]
```
Make count_ops() work with logic operations by creating a binary tree. Bug was that Logic functions are not the instance of sympy.core.expr.Expr due to which logic operation were actually skipping to "else" case.
Fixes #7010
Added tests of the logic functions for count_ops() function.