Fixed reading DateTimeField for Django 1.3

Fixed Django 1.5 warning about admin media.
Fixed reading DateTimeField for values with milisecond resolution.

Previously it raised ValueError. Added test.
Fixed all tests to restore db status before Assert

It is safer because future tests will not be breaken if the assert fails.
Added support for Django 1.6b1

- Requires new manage.py,
- Django 1.6 SQLCompiler has some modified methods and attributes
- More parameters to field_cast_sql
Added support for Django 1.6b2

Created an empty driver that emulates parts of DB API2 required by Django 1.6.
It should also define some Error classes.
Fixed TimeField for read and save.

This previously raised a ValueError. Added test.
Added support for read only fields like Lead.Name or LastModifiedBy.

These fields can be used in the model with the parameter
`sf_read_only=models.READ_ONLY`, but the backend knows the field shouldn't be
saved. Previously the field couldn't be used in the model or that model
couldn't be saved.
Added tests for read only fields.
Added a customized inspectdb command for salesforce backend.

The command 'python manage.py inspectdb --database=salesforce' exports
a complete valid structure of Salesforce database for models.py that can
be used unmodified to read and write all retriveable objects, including
recognition of relations between them or read only fields recognition.
Added hynekcer to AUTHORS list
updates primarily to the tests, and testsrunner

(Rebased to the rurrent branch and splitted to more commits by hynekcer.)
Improvement to query delete for nested WhereNodes.

(Rebased to the current branch and splitted to more commits by hynekcer.)
Some code from sbussetti's commit is omitted because not actual in this branch.
Fixed switch PERSON_ACCOUNT_ACTIVATED for it not activated
Added warning for unsupported values of on_delete
Fixed operators LIKE '%...%' and similar
Fixed all test to be more readable and robust by function refresh(obj)

I found that "test_unicode" didn't test anything, because it compared an old
object. Restoring the db status was not readable (bug free) without try/finally
Added test for a general custom object with a char field.
Refactored extract_values function to be DRY, due to the next commit.

This code does exactly the same as previously.
Support for some default ForeignKey field specified by Salesforce.

Previously was more complicated inserting some simple object.
Added error report for unsupported bulk_create.