Add doc about facets without observations, add 3 examples and do some cleanup (#589)

* Updating Data Sources pages

* first drafts of entity import

* more work on entities

* continued work

* continued work

* allow sample API key

* more work

* more work on entities

* more work

* more changes

* more changes

* split out custom entities into a separate file

* start work on Python v2 docs

* start of new Python docs

* create all pages for directory and more work on landing page

* more work

* add skeleton files

* rename old Python docs

* fix mistaken files

* fix files again

* fix more files

* remove template from PR

* changed examples to directly print responses

* move pagination out of main page and into node page

* wording change suggested by Jorge

* fixed response formatting object wording, per Jorge

* new node page

* start work on resolve

* work on observations

* more work

* work on observations

* add another observation example, add TOCs, and simplify some text

* remove files from branch

* remove file from branch

* Revert "remove file from branch"

This reverts commit b886562.

* Revert "remove files from branch"

This reverts commit 0c4ff6c.

* Revert "work on observations"

This reverts commit 1493581.

* revert all Python changes from this branch

* try again

* remove template from this branch

* slight word change

* changes

* added description of select=facet and 2 more examples

* small formatting fixes

* reformat truncated responses

* try again to reformat

* try again to reformat

* try again to reformat

* removed duplicate example

* changed entities to make examples shorter

* fix format glitch

* get extraneous file out of PR

* remerging

* fast forward

* fix node file yet again

Author: kmoscoe

api/rest/v2/node.md

@@ -61,7 +61,7 @@ JSON data:
 <script src="/assets/js/syntax_highlighting.js"></script>
 <script src="/assets/js/api-doc-tabs.js"></script>
 
-## Query parameters
+### Query parameters
 
 | Name                                                  | Type   |  Description           |
 | ----------------------------------------------------- | ------ | -----------------------|
@@ -109,7 +109,7 @@ The response looks like:
 
 ### Example 1: Get all property labels for a given node
 
-Get all (incoming arc) property labels of the node with DCID `geoId/06` by querying all properties with the `<-` symbol. This returns just the property labels but not the property values.
+Get all (incoming arc) property labels of the node with DCID `geoId/06` (California) by querying all properties with the `<-` symbol. This returns just the property labels but not the property values.
 
 Parameters:
 {: .example-box-title}
@@ -210,8 +210,7 @@ Response:
 ### Example 3: Get the DCIDs of all the states in the United States
 
 In this example, we use a [filter expression](/api/rest/v2/#filters) to specify "all contained places in
-[United States](https://datacommons.org/browser/country/USA){: target="_blank"} (DCID `country/USA`) of
-type `State`".
+United States of type `State`".
 
 Parameters:
 {: .example-box-title}