Wrapg

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Added
- Added create_database() function

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Added
- Added common.py in tests

Changes
- Broke some more complex tests like for upsert() to specific files for better organization.

Fixed
- Reverted code for colname_snip() as it was not allowing for auto-index creation. '::' is not allowed in index name.

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Fixed
- Fix snippet module refernce to iterable_difference. from wrapg import util vs from util import iterable_difference.

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Added
- Add more tests for wrapg functions
- Add exclude_update parameter to update() and upsert() functions

Fixed
- Fix colname_snip() to properly cast types if date() passed; it was affecting upsert with index=False
- Fixed exisitng snippet tests due to type casting issue on colname_snip()

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Added
- Add insert_snip() to resuse insert code
- Improve regex to better detect functions in column
- Add 'use_index' to upsert(); set to False to upsert without use of unique index
- Add more tests on util.py and snippet.py

Fixed
- Fix sqlfunc() to properly cast a timestamp to date()
- Fix update() with ' AND '

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Added
- Add code for delete() which takes dictionary for where clause parmeters
- The column name can be wrapped with sql function like upsert and update functions
- Add clear_table() to quickly clear all data in specified table