Factor Maryland jurisdiction lists to separate module

Move county and congressional district lists to
``openelex.us.md.jurisdiction`` instead of being a class attribute
of an ad-hoc class in ``us.md.validate``.

Addresses https://github.com/openelections/core/issues/104
Validate 2000 general election result counts

Add state legislative districts to ``us.md.jurisdiction``.

Add ``election_id`` attribute to election description class and
change functon signatures to use this attribute rather than passing
the election id explicitely.

Validate the number of results on a reporting level basis.

Reorganize the code, grouping helper functions, election-specific
validators, and general validators.

Addresses https://github.com/openelections/core/issues/36
Document ad-hoc API for election description classes

Addresses https://github.com/openelections/core/issues/36
us.md.validate as package

I want to load expected candidate counts from a CSV fixture and
want to package it in the validate directory.

Addresses https://github.com/openelections/core/issues/36
Add validation for 2002 Maryland primary

This required a lot of changes.

First, because there were State Senate and House of Delegates
contests, there were a ton of candidates.  I set up a mechanism to
load the candidate counts from a fixture.

I also added lists and mappings for the State Senate and House of
Delegates to ``us.md.jurisdictions``.

The mappings from Congressional District to county changed from
2000 to 2002, so I had to define these differently in
``us.md.jurisdictions``.

Finally, I changed the keys in district mappings from integers to
strings.

Addresses https://github.com/openelections/core/issues/36
Refactor validation classes

Add contest, candidate and result count validations for the 2002
general election.

To make the code more DRY, factor the counting methods into common
methods that handle both the primary and general election and move
these to the base ``MDElection`` class.

Move the election classes to a separate
``openelex.us.md.validate.election`` module.

Rename the validation helper classes ElectionYYYY[General|Primary]
instead of [General|Primary]YYYYElection to make the base class
names clearer.

Make the validation helper functions into methods of the
``MDElection`` class.

Addresses https://github.com/openelections/core/issues/36
Maryland 2004 contest, candidate and result count validation

Add validators for contest, candidate and result counts for the
2004 primary and general elections.

Move some common functionality shared between elections into
mixin classes.

2004's general election includes results for the Baltimore City
Comptroller office, but this isn't identified by a separate office
string.  Add a validator to detect this and a transform to remove
the records.

oAddresses https://github.com/openelections/core/issues/36
Allow running all transforms for a state

I think I introduced this as a regression when I refactored the
way validations were selected and run.
Validate contest, candidate and result counts for MD 2006 primary

Addresses https://github.com/openelections/core/issues/36
Strip leading/trailing whitespace from legislative headers

Results for the 01A House of Delegates district were getting
skipped because the column in the 2006 primary state legislative
results CSV has a leading whitespace, i.e. " LEGS 01A".