Upgraded third party Python libraries to latest versions.

(Redmine issue: #3387,#5062)

conf/requirements.pip

 python-dotenv==0.10.3
-pytz==2019.1
+pytz==2019.2
 ply==3.11
 psycopg2==2.8.3
 babel==2.7.0
 wtforms==2.2.1
-sqlalchemy==1.3.5
-alembic==1.0.10
+sqlalchemy==1.3.8
+alembic==1.1.0
 jinja2==2.10.1
 blinker==1.4
 bsddb3==6.2.6
-flask==1.0.3
+flask==1.1.1
 flask-login==0.4.1
 flask-mail==0.9.1
 flask-migrate==2.5.2
@@ -24,9 +24,9 @@ dnspython==1.16.0
 geoip2==2.9.0
 requests==2.22.0
 rrdtool==0.1.15
-pyyaml==5.1.1
+pyyaml==5.1.2
 pydgets==0.9
-pyzenkit==0.54
+pyzenkit==0.56
 pynspect==0.17
 ipranges==0.1.10
 typedcols==0.1.13

pyzenkit @ 539cfc4b

-Subproject commit 0822cbca7e37426fe90e37107f91a5e59696d822
+Subproject commit 539cfc4b20c51b589337d5821e8ad1128ea1c1ce