Conflation of namespace and feedId in RDBMS

[landonreed]

There are a number of instances in the RDBMS code path where the variable name feedId is used to describe the SQL schema used to namespace feeds stored in the relational database (the format looks something like wxyz_abcdefghij.stops). This could be a bit confusing because feedId is also used frequently in Conveyal's software to mean the field found in the feed_info.txt file. We should first determine how to name this variable (e.g. should we just default to namespace with some parenthetical clarifying its use relative to a feed) and then clean up the files that contain this confusing usage.

Here's an instance where this issue is apparent:

gtfs-lib/src/main/java/com/conveyal/gtfs/GTFS.java

Line 35 in 892838d

public static FeedLoadResult export (String feedId, String outFile, DataSource dataSource, boolean fromEditor) {