List all importers and exporters

docs/src/exporter/README.md

@@ -2,6 +2,6 @@
 
 ## GraphML
 
-Module name: `export_graphml`
+Format name: `graphml`
 
-TODO
+Exports files as [GraphML](http://graphml.graphdrawing.org/) files which conform to the [graphANNIS data model].

docs/src/importer/README.md

@@ -1,37 +1,58 @@
 # Importer
 
+## CONLL-U
+
+Format name: `conllu`
+
+Import files in the [CONLL-U
+format](https://universaldependencies.org/format.html) from the Universal
+Dependencies project.
+
+
+## EXMARaLDA
+
+Format name: `exmaralda`
+
+Import [EXMARaLDA partition
+editor](https://exmaralda.org/en/partitur-editor-en/) (`.exb`) files.
+
 ## GraphML
 
 Format name: `graphml`
 
-Imports files in the graphANNIS 
+Imports files in the [GraphML](http://graphml.graphdrawing.org/) file which have
+to conform to the [graphANNIS data model].
 
-## CONLL-U
+## Meta
 
-Module name: `import_conllu`
+Format name: `meta`
 
-TODO
+Works similar to the Pepper configuration value
+[`pepper.before.readMeta`](https://corpus-tools.org/pepper/generalCustomizationProperties.html)
+and imports metadata property files for documents and corpora by using the file
+name as path to the document.
 
-## EXMARaLDA
+## None
 
-Module name: `import_exmaralda`
+Format name: `none`
 
-TODO
+A special importer that imports nothing.
 
 ## PTB
 
-Module name: `import_ptb`
+Format name: `ptb`
 
-TODO
+Imports files in the Penn Treebank (bracket) format.
 
 ## TextGrid
 
-Module name: `import_textgrid`
+Format name: `textgrid`
 
-TODO
+Imports [Praat TextGrid text file format](https://www.fon.hum.uva.nl/praat/manual/TextGrid_file_formats.html).
 
-## Spreadsheat (Excel-like)
+## Excel-like
 
-Module name: `import_spreadsheet`
+Format name: `xlsx`
 
-TODO
+Imports Excel Spreadsheets where each line is a token, the other columns are
+spans and merged cells can be used for spans that cover more than one token.