Use indices in testing whether on
a boundary. This is done to avoid using the upper and lower coordinate extents
in this check as floats equality comparison is not safe."
initial hacking to add flags for boundaries
add flags to the grid and dimension
objects to indicate whether the grid is on boundary
use on_lower_boundaries and on_upper_boundaries grid
flags in the methods apply_q_bcs and apply_aux_bcs instead of
making indices comparison
correct spelling error
Merge pull request #220 from amal-ghamdi/add_bc_flags

solution for issue #154, adding boundary flags
Removed indices property. Removed boundary check from euler_2D app because the q_apply_bc in the solver does the check already
Merge pull request #221 from amal-ghamdi/issue_154_cont

Continue sol for issue #154: Removed indices property.
Change documentation toctree to use 3 levels of hierarchy.
Consolidate and improve solvers documentation.
Merge pull request #222 from ketch/doc-sharpclaw

Update and reorganize docs
Update link to SharpClaw documentation.
Merge pull request #223 from ketch/doc-sharpclaw

Update link to SharpClaw documentation.