Add exactly1 option for disjunctions and fix bugs

[pulsipher]

Closes #72. Some minor bug fixes and changes that came up include:

• Have deletion methods for disjunctions and disjunct constraints remove all their mappings
• Remove unnecessary GDPData(args...) method
• Include the macro docstrings in the docs
• Moving reformulation specific methods
• Fixing the reformulation methods for exactly constraints to better handle assumptions on function type (more work is needed)
• Improved error messaging for incorrect keyword arguments to @disjunction
• Fixed some test functions to use @test on the first call of a method/macro to be tested which leads to more helpful error messages when it doesn't work (more work is needed to do this with all tests)

[codecov]

Codecov Report

Attention: 2 lines in your changes are missing coverage. Please review.

Comparison is base (3af182e) 98.91% compared to head (50cdc2a) 98.84%.

Additional details and impacted files

@@            Coverage Diff             @@
##           master      #90      +/-   ##
==========================================
- Coverage   98.91%   98.84%   -0.07%     
==========================================
  Files          10       10              
  Lines         921      952      +31     
==========================================
+ Hits          911      941      +30     
- Misses         10       11       +1     

Files	Coverage Δ
src/bigm.jl	100.00% <100.00%> (ø)
src/constraints.jl	98.83% <100.00%> (+0.19%)	⬆️
src/datatypes.jl	100.00% <ø> (ø)
src/hull.jl	100.00% <100.00%> (ø)
src/logic.jl	99.25% <100.00%> (+<0.01%)	⬆️
src/macros.jl	96.89% <ø> (+0.77%)	⬆️
src/reformulate.jl	100.00% <100.00%> (ø)
src/model.jl	93.33% <33.33%> (-6.67%)	⬇️

☔ View full report in Codecov by Sentry.
📢 Have feedback on the report? Share it here.

[hdavid16]

I think we should use a different name for this keyword argument since it is not exactly 1 for Nested disjunctions.

[pulsipher]

I think we should use a different name for this keyword argument since it is not exactly 1 for Nested disjunctions.

Any suggestions?