Add BaseLayer toggle widget & default base layers

Pull Request Test Coverage Report for Build 1394

120 of 351 (34.19%) changed or added relevant lines in 12 files are covered.
514 unchanged lines in 15 files lost coverage.
Overall coverage decreased (-11.8%) to 38.061%

Changes Missing Coverage	Covered Lines	Changed/Added Lines	%
utils/src/main/java/io/ona/kujaku/utils/Constants.java	0	1	0.0%
library/src/main/java/com/mapbox/mapboxsdk/style/layers/ExposedLayoutPropertyValue.java	0	2	0.0%
library/src/main/java/io/ona/kujaku/KujakuLibrary.java	0	2	0.0%
library/src/main/java/io/ona/kujaku/exceptions/InvalidStyleStateException.java	0	2	0.0%
library/src/main/java/io/ona/kujaku/plugin/switcher/layer/SatelliteBaseLayer.java	18	22	81.82%
library/src/main/java/io/ona/kujaku/plugin/switcher/ExpressionArrayLiteral.java	0	9	0.0%
library/src/main/java/io/ona/kujaku/plugin/switcher/BaseLayerSwitcherPlugin.java	42	83	50.6%
library/src/main/java/io/ona/kujaku/plugin/switcher/layer/StreetsBaseLayer.java	0	42	0.0%
library/src/main/java/io/ona/kujaku/utils/LayerUtil.java	53	112	47.32%
library/src/main/java/io/ona/kujaku/plugin/switcher/layer/BaseLayer.java	4	73	5.48%
<!--	Total:	120	351	34.19%	-->

Files with Coverage Reduction	New Missed Lines	%
library/src/main/java/io/ona/kujaku/exceptions/WmtsCapabilitiesException.java	2	0.0%
utils/src/main/java/io/ona/kujaku/utils/exceptions/OfflineMapDownloadException.java	2	0.0%
library/src/main/java/io/ona/kujaku/helpers/MapboxLocationComponentWrapper.java	3	0.0%
sample/src/main/java/io/ona/kujaku/sample/repository/BaseRepository.java	5	0.0%
library/src/main/java/io/ona/kujaku/wmts/model/WmtsLayer.java	5	75.0%
library/src/main/java/io/ona/kujaku/KujakuLibrary.java	8	0.0%
library/src/main/java/io/ona/kujaku/domain/Point.java	12	0.0%
sample/src/main/java/io/ona/kujaku/sample/MyApplication.java	14	0.0%
library/src/main/java/io/ona/kujaku/data/MapBoxDeleteTask.java	18	21.62%
sample/src/main/java/io/ona/kujaku/sample/repository/KujakuRepository.java	24	0.0%
<!--	Total:	514	-->