Enable arrow line and boundary layers to be updated

[ekigamba]

Fixes #277

[coveralls]

Pull Request Test Coverage Report for Build 1310

• 38 of 126 (30.16%) changed or added relevant lines in 6 files are covered.
• 6 unchanged lines in 2 files lost coverage.
• Overall coverage increased (+0.4%) to 33.269%

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Changes Missing Coverage	Covered Lines	Changed/Added Lines	%
library/src/main/java/io/ona/kujaku/views/KujakuMapView.java	1	10	10.0%
library/src/main/java/io/ona/kujaku/layers/BoundaryLayer.java	16	27	59.26%
library/src/main/java/io/ona/kujaku/layers/ArrowLineLayer.java	19	35	54.29%
sample/src/main/java/io/ona/kujaku/sample/activities/FociBoundaryActivity.java	0	24	0.0%
sample/src/main/java/io/ona/kujaku/sample/activities/CaseRelationshipActivity.java	0	28	0.0%
<!--	Total:	38	126	30.16%	-->

Files with Coverage Reduction	New Missed Lines	%
library/src/main/java/io/ona/kujaku/views/KujakuMapView.java	2	28.98%
sample/src/main/java/io/ona/kujaku/sample/activities/CaseRelationshipActivity.java	4	0.0%
<!--	Total:	6		-->

Totals
Change from base Build 1279:	0.4%
Covered Lines:	1722
Relevant Lines:	5176

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💛 - Coveralls

[githengi]

Rename to Disable arrows showing relationship button to Disable/Remove Arrows, otherwise one button should be on top of another.

[ekigamba]

Stacked the buttons and changed button text