Add indexes and support for fetching analytics data for single dataset

[Zharktas]

Adds indexes for search terms table with migration.
Add cli support to fetch analytics data for only single dataset.
Uses filter pattern in dataset page views for pre-filterning non-dataset urls.

[coveralls]

Pull Request Test Coverage Report for Build 7751929216

• -40 of 46 (13.04%) changed or added relevant lines in 3 files are covered.
• 4 unchanged lines in 2 files lost coverage.
• Overall coverage decreased (-0.3%) to 42.035%

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Changes Missing Coverage	Covered Lines	Changed/Added Lines	%
ckanext/matomo/cli.py	2	3	66.67%
ckanext/matomo/matomo_api.py	3	12	25.0%
ckanext/matomo/commands.py	1	31	3.23%

Files with Coverage Reduction	New Missed Lines	%
ckanext/matomo/commands.py	1	7.82%
ckanext/matomo/matomo_api.py	3	20.0%

Totals
Change from base Build 7723504636:	-0.3%
Covered Lines:	599
Relevant Lines:	1425

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💛 - Coveralls