Seed should follow naming of the tns-core-modules files

[PeterStaev]

Currently the seed uses naming different than the ones that are used through in the tns-core-modules. Using similar names will make it easier for people to also navigate (and possibly contribute) to the main Nativescript repo. So:

• index.d.ts should become <name-of-plugin>.d.ts
• <name-of-plugin>.common.ts should become <name-of-plugin>-common.ts
• the Common class should be named just named <NameOfPlugin>

Also the platform specific files should have export * from './<name-of-plugin>-common.ts'

[PeterStaev]

also the class that is in the .d.ts file should be just export class <NameOfPlugin> instead of export declare class