Upgrade Docker image to Alpine 3.11

This make tesseract 4.1 avaialbe, which fixes some things like infinite
processing loops on some documents:
tesseract-ocr/tesseract#2288 (comment)

Some dependencies had to be bumped for being compatible with the new Alpine
libraries.

Dockerfile

@@ -1,4 +1,4 @@
-FROM alpine:3.10
+FROM alpine:3.11
 
 LABEL maintainer="The Paperless Project https://github.com/the-paperless-project/paperless" \
       contributors="Guy Addadi <[email protected]>, Pit Kleyersburg <[email protected]>, \
@@ -67,4 +67,4 @@ COPY data/ /usr/src/paperless/data/
 COPY media/ /usr/src/paperless/media/
 
 # Collect static files
-RUN sudo -HEu paperless /usr/src/paperless/src/manage.py collectstatic --clear --no-input
+RUN sudo -HEu paperless /usr/src/paperless/src/manage.py collectstatic --clear --no-input