Implement mbtiles support

[githengi]

Resolves #321

[coveralls]

Pull Request Test Coverage Report for Build 1536

• 187 of 303 (61.72%) changed or added relevant lines in 5 files are covered.
• 1 unchanged line in 1 file lost coverage.
• Overall coverage increased (+1.02%) to 53.227%

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Changes Missing Coverage	Covered Lines	Changed/Added Lines	%
library/src/main/java/io/ona/kujaku/plugin/switcher/layer/MBTilesLayer.java	26	31	83.87%
library/src/main/java/io/ona/kujaku/mbtiles/MBTilesHelper.java	90	96	93.75%
library/src/main/java/io/ona/kujaku/mbtiles/MbtilesFile.java	33	54	61.11%
library/src/main/java/io/ona/kujaku/views/KujakuMapView.java	3	24	12.5%
library/src/main/java/io/ona/kujaku/mbtiles/TileHttpServer.java	35	98	35.71%
<!--	Total:	187	303	61.72%	-->

Files with Coverage Reduction	New Missed Lines	%
library/src/main/java/io/ona/kujaku/views/KujakuMapView.java	1	23.63%
<!--	Total:	1		-->

Totals
Change from base Build 1525:	1.02%
Covered Lines:	3043
Relevant Lines:	5717

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💛 - Coveralls