WebsocketProvider improvements

[nivida]

Description

Fixes #2711 #2851

Type of change

• Bug fix

Checklist:

• I have selected the correct base branch.
• I have performed a self-review of my own code.
• I have commented my code, particularly in hard-to-understand areas.
• I have made corresponding changes to the documentation.
• My changes generate no warnings.
• I have updated or added types for all modules I've changed
• Any dependent changes have been merged and published in downstream modules.
• I ran npm run test in the root folder with success and extended the tests if necessary.
• I ran npm run build in the root folder and tested it in the browser and with node.
• I ran npm run dtslint in the root folder and tested that all my types are correct
• I have tested my code on an ethereum test network.

[boomfly]

AbstractSocketProvider.js 169 line:
this.removeAllListeners();
this line removes all app defined provider listeners, so we can't receive 'connect', 'reconnected', 'error' events any more

[boomfly]

removed import isFunction in AbstractSubscription so on line 167, 180 undefined exception

[boomfly]

All other seems fine. I hope this PR merged. I need it very much

[nivida]

@boomfly Yes, I'll fix all of these. I'm currently testing the reconnecting of the socket connection with different edge cases etc. I will tag you for a final review later:)

[coveralls]

Coverage decreased (-0.1%) to 95.743% when pulling c8ba201 on fix/websocket-reconnecting into c3f4845 on 1.0.

[coveralls]

Coverage decreased (-0.1%) to 95.743% when pulling c8ba201 on fix/websocket-reconnecting into c3f4845 on 1.0.

[coveralls]

Coverage decreased (-0.1%) to 95.743% when pulling c8ba201 on fix/websocket-reconnecting into c3f4845 on 1.0.