searching the Physics Derivation Graph database

The Physics Derivation Graph database is just a JSON file, so searching a plain text file is easy. However, the value of search is in the relations, not just finding a match. 

There are multiple aspects of the Physics Derivation Graph database to search: symbols, units, dimensions, inference rules, symbol names, operators. 

A workflow for search is

1. user searches web interface for "x"
2. the search interface returns multiple rows of a table; something like

   symbol ID	symbol	name	dimension	units
   948294	x_m	asdf	L:0,T:1,M:0
   113942	y_x	mimi	L:-1,T:0,M:0	Kg
   501901	XM	minX	L:0,T:2,M:1	seconds^2

3. if the user selects one of the symbols, then
4. the search interface shows which expressions contain that symbol
5. if the user selects one of the expressions, then
6. the search interface shows which derivations contain that expression

Currently, the search of symbols ( https://derivationmap.net/list_all_symbols ) is separate from the search of expressions ( https://derivationmap.net/list_all_expressions ) though the two are hyperlinked in both directions.