Fix init_session(ipython=False) for non-unicode terminals.

InteractiveConsole is another case were we should not force
use_unicode=True. Instead, let's rely on the code that checks
sys.stdout.encoding to automatically set this to the correct
value.
init_printing: Update a comment.
A new utility for integrals
Added support for summations in finit diff
Removed integral change
finite diff function that works for multiple indexes
Wrapped the docstrings
Print unnamed Dummy symbols more prominently

Previously, they were just printed as _12 or pretty printed as just 12, which
looked like a number in an expression.  This way, if a Dummy leaks out, it is
clear.
in latex: don't use operatorname for single letter functions; properly render functions without arguments
fix quantum printing tests
fix docstring
refactor logic for printing functions in latex. Add logic for printing
user-defined functions without arguments. This does not work for
functions built in to SymPy (e.g., sin, cos, gamma).

Non-greeks could be easily added with a method _print_FunctionClass.
This would not do the right thing for the gamma function, though.
tests for latex changes
fix latex printing of some built-in functions without arguments
(failing) tests for some issues with the latex printing module
more greek printing fixes
Merge pull request #2127 from SaurabhJha/kauers

Kauers
Made finite_diff efficient
Fix issue 3700

- Manualintegrate changes:
    - Rewrite rule: do not use if integrand cannot be evaluated with manualintegrate
    - Substitution rule: do not use ConstantTimesRule if constant == 1
    - Added test
Fix typos in usage of manualintegrate in _eval_integral