[core] Switch update interval parameter to seconds

As correctly pointed out by @rrhuffy, restricting update intervals to
minutes is pretty arbitrary. Therefore, change logic to specify updates
intervals in *seconds*.

Also, to maintain backwards compatibility for users that already have
custom intervals in their config, allow a module to specify their own
"factor" for intervals. So a module that expects the interval to be in
minutes can set the factor to 60.

bumblebee/modules/apt.py

@@ -44,6 +44,7 @@ class Module(bumblebee.engine.Module):
     def __init__(self, engine, config):
         widget = bumblebee.output.Widget(full_text=self.updates)
         super(Module, self).__init__(engine, config, widget)
+        self.interval_factor(60)
         self.interval(30)
 
     def updates(self, widget):

bumblebee/modules/currency.py

@@ -37,6 +37,7 @@ class Module(bumblebee.engine.Module):
             bumblebee.output.Widget(full_text=self.price)
         )
         self._data = []
+        self.interval_factor(60)
         self.interval(1)
         self._base = self.parameter("source", "GBP")
         self._symbols = self.parameter("destination", "USD,EUR").split(",")

bumblebee/modules/dnf.py

@@ -52,6 +52,7 @@ class Module(bumblebee.engine.Module):
     def __init__(self, engine, config):
         widget = bumblebee.output.Widget(full_text=self.updates)
         super(Module, self).__init__(engine, config, widget)
+        self.interval_factor(60)
         self.interval(30)
 
     def updates(self, widget):

bumblebee/modules/github.py

@@ -25,6 +25,7 @@ class Module(bumblebee.engine.Module):
                                      bumblebee.output.Widget(full_text=self.github)
                                     )
         self._count = 0
+        self.interval_factor(60)
         self.interval(5)
         self._requests = requests.Session()
         self._requests.headers.update({"Authorization":"token {}".format(self.parameter("token", ""))})

bumblebee/modules/stock.py

@@ -29,6 +29,7 @@ class Module(bumblebee.engine.Module):
         self._symbols = self.parameter('symbols', '')
         self._change = bumblebee.util.asbool(self.parameter('change', True))
         self._value = None
+        self.interval_factor(60)
         self.interval(60)
 
     def value(self, widget):

bumblebee/modules/weather.py

@@ -42,6 +42,7 @@ class Module(bumblebee.engine.Module):
         self._showcity = bumblebee.util.asbool(self.parameter("showcity", True))
         self._unit = self.parameter("unit", "metric")
         self._valid = False
+        self.interval_factor(60)
         self.interval(15)
 
         engine.input.register_callback(self, button=bumblebee.input.LEFT_MOUSE, cmd=self._next_location)