Add test data and tests for titer models

Adds test data based on public titer data and sequences from the
measurements panel paper [1] and adds functional tests for basic titer
model commands and the new commands with attribute prefixes.

[1] https://github.com/blab/measurements-panel/tree/main/data

tests/functional/titers/cram/titers-sub-with-tree-and-custom-prefix.t

@@ -0,0 +1,20 @@
+Setup
+
+  $ pushd "$TESTDIR" > /dev/null
+  $ export AUGUR="${AUGUR:-../../../../bin/augur}"
+
+Test titer substitution model with alignment and tree inputs and a custom prefix for the node data attributes in the output.
+
+  $ ${AUGUR} titers sub \
+  >   --tree ../data/tree.nwk \
+  >   --titers ../data/titers.tsv \
+  >   --alignment ../data/aa_seq_HA1.fasta \
+  >   --gene-names HA1 \
+  >   --attribute-prefix custom_prefix_ \
+  >   --output $TMP/titers-sub.json > /dev/null
+  Read titers from ../data/titers.tsv, found:
+   --- 61 strains
+   --- 15 data sources
+   --- 232 total measurements
+  $ grep custom_prefix_cTiterSub $TMP/titers-sub.json | wc -l
+  \s*120 (re)

tests/functional/titers/cram/titers-sub-with-tree.t

@@ -0,0 +1,19 @@
+Setup
+
+  $ pushd "$TESTDIR" > /dev/null
+  $ export AUGUR="${AUGUR:-../../../../bin/augur}"
+
+Test titer substitution model with alignment and tree inputs.
+
+  $ ${AUGUR} titers sub \
+  >   --tree ../data/tree.nwk \
+  >   --titers ../data/titers.tsv \
+  >   --alignment ../data/aa_seq_HA1.fasta \
+  >   --gene-names HA1 \
+  >   --output $TMP/titers-sub.json > /dev/null
+  Read titers from ../data/titers.tsv, found:
+   --- 61 strains
+   --- 15 data sources
+   --- 232 total measurements
+  $ grep cTiterSub $TMP/titers-sub.json | wc -l
+  \s*120 (re)

tests/functional/titers/cram/titers-tree-with-custom-prefix.t

@@ -0,0 +1,18 @@
+Setup
+
+  $ pushd "$TESTDIR" > /dev/null
+  $ export AUGUR="${AUGUR:-../../../../bin/augur}"
+
+Test titer tree model with a custom prefix for the node data attributes in the output.
+
+  $ ${AUGUR} titers tree \
+  >   --tree ../data/tree.nwk \
+  >   --titers ../data/titers.tsv \
+  >   --attribute-prefix custom_prefix_ \
+  >   --output $TMP/titers-tree.json > /dev/null
+  Read titers from ../data/titers.tsv, found:
+   --- 61 strains
+   --- 15 data sources
+   --- 232 total measurements
+  $ grep custom_prefix_cTiter $TMP/titers-tree.json | wc -l
+  \s*120 (re)

tests/functional/titers/cram/titers-tree.t

@@ -0,0 +1,17 @@
+Setup
+
+  $ pushd "$TESTDIR" > /dev/null
+  $ export AUGUR="${AUGUR:-../../../../bin/augur}"
+
+Test titer tree model.
+
+  $ ${AUGUR} titers tree \
+  >   --tree ../data/tree.nwk \
+  >   --titers ../data/titers.tsv \
+  >   --output $TMP/titers-tree.json > /dev/null
+  Read titers from ../data/titers.tsv, found:
+   --- 61 strains
+   --- 15 data sources
+   --- 232 total measurements
+  $ grep cTiter $TMP/titers-tree.json | wc -l
+  \s*120 (re)