[7_1_X][TIMOB-25591] Android: Programmatically check whether app has notification permission on Android.

[ypbnv]

JIRA: https://jira.appcelerator.org/browse/TIMOB-25591

Description:
Backport of:#9669

[build]

	Messages
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[hansemannn]

We should really refactor the Android notifications namespace..For example, remoteNotificationsEnabled is very similar, but developers need to curate two pairs of APIs.

[ypbnv]

@hansemannn Can we find a common ground between iOS and Android notifications systems? I am not familiar with the former enough. Does it have a separation between local and remote notifications? Maybe we can create Ti.Notifications namespace where we could transfer Android's Notification, NotificationChannel and NotificationManager namespaces, combine what they have in common with iOS?

[lokeshchdhry]

FR Passed.

areNotificationsEnabled() works as expected.

1. Notifications are enabled by default & areNotificationsEnabled() returns true.
2. After turning off notifications in settings for the app areNotificationsEnabled() returns false.

Studio Ver: 5.0.0.201712081732
SDK Ver: 7.1.0 local build
OS Ver: 10.13.2
Xcode Ver: Xcode 9.2
Appc NPM: 4.2.12
Appc CLI: 7.0.2
Daemon Ver: 1.0.1
Ti CLI Ver: 5.0.14
Alloy Ver: 1.11.0
Node Ver: 8.9.1
NPM Ver: 5.5.1
Java Ver: 1.8.0_101
Devices: ⇨ google Nexus 6P --- Android 8.0.0
⇨ google Nexus 5 --- Android 6.0.1
Emulator: Android 4.1