Support component hooks

[mr-cal]

What needs to get done

snapcraft.yaml syntax

Support the following syntax:

components:
  <component-name>:
    hooks:
      <hook-name>:
        plugs:
          - <plug-name>
        <all-currently-valid-hooks>

Supported hooks are:

• install
• pre-refresh
• post-refresh
• remove

meta/snap.yaml syntax

The meta/snap.yaml needs to list all component metadata, including the component hooks. Currently, this is not happening.

Why it needs to get done

To support component hooks