Streamline/simplify project onboarding

[oleg-nenashev]

As we discovered there is conflicting information in the TOC documentation, including the requirements to the incubating projects and the onboarding flow. It would be great to clean up the documentation so that the project could easily follow the onboarding pipeline.

Related issues

• Remove non-existent sandbox state Remove errant references to a Sandbox stage #98
• Remove duplication - Remove duplication of graduation criteria, update the proposals page #109
• Clarify IP policy IP policy #28
• Create new application template for incubating Create a new project onboarding template #115
• Create a new “How to join the CDF?” guide Create a new “How to join the CDF?” guide #166