feat(tabs): Add disabled tab + improvements

[trimox]

• Add disabled tab
• Fix [active] property changes not propagating Active mdc-tab #349
• Fix mdc-tab-bar-scroller__indicator misplaced issue mdc-tab-bar-scroller__indicator misplaced #281
• Remove mdc-tab-bar-scroll-button directive
• Update documentation + new examples
• Include unit testing

mdc-tab

• Add disabled: boolean property to mdc-tab
• Refactor active property
• Add changeDetection: ChangeDetectionStrategy.OnPush
• Add preserveWhitespaces: false
• Add getComputedWidth(): number; return the computed width for tab.
• Add getComputedLeft(): number; return the computed left offset for tab.
• Add isActive() return true if tab is active.
• Add setActive(boolean); set tab active property to value passed.
• Add getPreventDefaultOnClick(): boolean; return true if the tab prevents the default click action.
• Add setPreventDefaultOnClick(boolean); sets tabs preventDefaultOnClick property to the value passed.
• Add measureSelf(); sets computedWidth and computedLeft for a tab.

mdc-tab-bar

• Add getComputedWidth(): number
• Add layout(): void
• Add changeDetection: ChangeDetectionStrategy.OnPush
• Add preserveWhitespaces: false
• Add getActiveTabIndex(): number
• Add switchToTabAtIndex(index: number, shouldNotify: boolean = true)
• Add MdcTabBarIndicator directive
• Add setPreventDefaultOnClickForTabAtIndex(index: number, preventDefaultOnClick: boolean)
• Add isDefaultPreventedOnClickForTabAtIndex(index: number): boolean

mdc-tab-bar-scroller

• Add layout()
• Add changeDetection: ChangeDetectionStrategy.OnPush
• Add preserveWhitespaces: false
• Add scrollBack(event?: Event)
• Add scrollForward(event?: Event)
• Remove mdc-tab-bar-scroll-button directive

BREAKING CHANGE: Removed mdc-tab-bar-scroll-button directive. Use mdc-icon instead. Please update your code accordingly.
Example:

<mdc-tab-bar-scroll-back>
  <mdc-icon>navigate_before</mdc-icon>
</mdc-tab-bar-scroll-back>

Closes #349 Closes #147 Closes #281

[codecov]

Codecov Report

Merging #369 into master will increase coverage by 0.3%.
The diff coverage is 96.17%.

@@           Coverage Diff            @@
##           master    #369     +/-   ##
========================================
+ Coverage    92.6%   92.9%   +0.3%     
========================================
  Files          90      90             
  Lines        4910    4992     +82     
  Branches      903     916     +13     
========================================
+ Hits         4547    4638     +91     
+ Misses        363     354      -9

Impacted Files	Coverage Δ
src/lib/tabs/index.ts	100% <ø> (ø)	⬆️
src/lib/tabs/tab-bar-scroller/tab-bar-scroller.ts	89.54% <100%> (+2.04%)	⬆️
src/lib/tabs/tab-bar/tab-bar.ts	92.85% <93.5%> (+1.34%)	⬆️
src/lib/tabs/tab/tab.ts	99.18% <97.95%> (+3.99%)	⬆️
src/lib/snackbar/snackbar.component.ts	91.48% <0%> (+3.54%)	⬆️

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[trimox]

All set. Finishing up some demo examples and will merge.